A changing of the guard at Switzerland's two biggest drugmakers is fuelling talk that Novartis may finally sell its multi-billion-dollar stake in cross-town rival Roche, potentially unlocking value for both sets of shareholders. The departure of Daniel Vasella after 17 years as chairman of Novartis and the forthcoming retirement of his adversary, Roche chairman Franz Humer, may prompt both sides to negotiate a sale that could boost earnings per share for each - and appease shareholders during a period of slower growth. "If Roche can buy this stake it's more positive for them than it is for Novartis, in terms of leverage on earnings. It's accretive for Novartis, but very accretive for Roche," said Jefferies' analyst Jeff Holford.